--- name: "xgterm" section: "1" platform: "linux" package: "xgterm" version: "2.2+dfsg-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/xgterm" --- # xgterm(1) terminal emulator for X with graphics and imaging capability ## NAME xgterm - terminal emulator for X with graphics and imaging capability ## SYNOPSIS **xgterm** \[-*toolkitoption* ...\] \[-*option* ...\] ## DESCRIPTION The *xgterm* program is a terminal emulator for the X Window System based largely on *xterm* but with a completely new graphics and imaging widget. It provides DEC VT102 and Tektronix 4014 compatible terminals for programs that can't use the window system directly. *XGterm* also serves as a prototype for the *Widget Server* being developed by the IRAF Project at NOAO. The *Object Manager Library* it uses implements a window system toolkit as an interpreted window-object language, allowing application GUIs to be defined and executed at runtime without compiling any code, and with minimal dependence upon the underlying window system toolkit library. We will concentrate here, however, on it's use as a terminal emulator and a description of the new *Gterm* widget. The Gterm graphics window operates almost identically to the *xterm* Tek window, however there are extensions for implementing full-screen cursors, imaging, area fills, colors, graphics erasure, a "status line" and so on. Any graphics application capable of running under an *xterm* Tek window should also be able to use *xgterm* as well. Client programs wishing to make use of the extended features, or those wishing to implement a GUI, are advised to use the OBM (*Object Manager*) library supplied with the XGterm source as part of the X11IRAF package. This provides a much better programmatic interface to all of the features available; however, as of this writing it is not yet fully documented. Users are referred to the *XImtool* task as an example of a more complex application using the *OBM Library* and *Gterm* widget, as well as demo tasks in the *guidemo* directory of the X11IRAF sources. The VT102 text window is unchanged from the original *xterm* application. All of it's resources, command-line options and operation are identical to that used by *xterm*. The *[termcap(5)](/termcap/5.md)* entry for *xterm* may be used for *xgterm* as well. See the *[xterm(1)](/xterm/1.md)* man page for details. ## OPTIONS All *[xterm(1)](/xterm/1.md)* and X Toolkit command line options are supported, there are no additional options. ## RESOURCES The program understands all of the core X Toolkit resource names and classes, all text window resources known to *[xterm(1)](/xterm/1.md)*, as well as the *Gterm* (graphics and imaging widget) resources. The proper Class name for all resources described here is *Gterm*. A table of available *Gterm* resources and their defaults may be found below, some of the more interesting resources are described here in detail: - *basePixel* Base cell of the custom colormap. This essentially allows you to reserve *basePixel* colors in the global colormap for other applications. The default is 38, if changed you'll need to also enable the *cmapInitialize* resource to force the Gterm widget to update it's global colormap resource in the X server. - *cmapInitialize* Initialize the ximtool colormap at startup. When resetting the *basePixel* resource or colormap this is required in order to force the Gterm widget to update it's global colormap resource in the X server. The default is False. - *cmapInterpolate* Interpolate the colormap to the number of display colors. The default is True. - *cmapName* Name used for private colormap. The default for all IRAF imaging applications is *image*. Gterm widget based imaging applications which have the same value of cmapName will share the same colormap, minimizing colormap flashing and allowing multiple applications to be run at the same time. - *color0* The widget background color. The default is black. - *color1* The widget foreground color. The default is white. - *color2* thru *color9* Optional drawing colors. The line color used for graphics is set using an escape sequence to select the current color index. See *Gterm I/O* *Escape Sequences* below for more details. - *crosshairCursorColor* Color of the full screen crosshair cursor. - *defaultMarker* Default marker type. Options include *text*, *line*, *polyline*, *rectangle*, *box*, *circle*, *ellipse*, and *polygon*. The default is *rectangle*. - *deiconifyWindow* De-iconify the Gterm graphics window when activated. The default is False. - *dialogBgColor* Dialog box (i.e. the status line) background color. Dialog text is text which is drawn into the dialog area at the bottom of the gterm window, it is transient and is not a permanent part of the graphics being drawn. Dialog text is normally used to interact with the user or to display messages during program operation, without affecting the graphics being drawn. - *dialogFgColor* Dialog box (i.e. status line) foreground color. - *ginmodeBlinkInterval* Graphics cursor blink interval, time is specified in milliseconds. The default is 0. - *ginmodeCursor* Graphics mode cursor type. The default is a full screen cursor custom to the widget. - *height* Height of the Gterm window. The default is 480. - *idleCursor* Cursor to use when not in graphics mode. The default is a plus sign. - *markerHighlightColor* Highlight color for the active marker. When the pointer moves into a marker is it marked "active", the highlight color and width change to which marker is active. The default is green. - *markerHighlightWidth* Highlight width for the active marker. The default is 2. - *maxColors* The maximum number of colors to use in the private global colormap, the default is 216. Out of this number 10 colors (the *color0* thru *color9* values) are reserved by the widget as static colors, the remainder may be allocated for images. - *raiseWindow* Raise the window when active. The default is False. - *warpCursor* Warp the cursor to the window when active. The default is False. - *width* Width of the Gterm window. The default is 640. ## GTERM WIDGET RESOURCES ### Class Hierarchy **Core -\> Gterm** ### Resources When creating a Gterm widget instance, the following resources are retrieved from the arguments list or from the resource database: | | | | | | --- | --- | --- | --- | | **Name** | **Class Type** | **Default** | **Description** | | alphaFont1 | XFontStruct | nil2 | Graphics fonts | | alphaFont2 | XFontStruct | 5x8 | " | | alphaFont3 | XFontStruct | 6x10 | " | | alphaFont4 | XFontStruct | 7x13 | " | | alphaFont5 | XFontStruct | 8x13 | " | | alphaFont6 | XFontStruct | 9x15 | " | | alphaFont7 | XFontStruct | 9x15 | " | | alphaFont8 | XFontStruct | 9x15 | " | | basePixel | Int | 38 | Base of private global colormap | | busyCursor | String | watch | Cursor to use when application is busy | | busyCursorBgColor | Foreground | white | Busy cursor background color | | busyCursorFgColor | Foreground | black | Busy cursor foreground color | | cacheRasters | String | whenNeeded | Save rasters as server pixmaps for faster access | | cmapInitialize | Boolean | False | Initialize colormap at startup | | cmapInterpolate | Boolean | True | Interpolate colormap | | cmapName | String | default | Custom colormap name | | cmapShadow | Int | 10 | Colormap shadow interval | | cmapUpdate | Int | 60 | Colormap update interval | | color0 | Background | black | Default graphics background color | | color1 | Foreground | white | Default graphics foreground color | | color2 | Foreground | red | Optional drawing color | | color3 | Foreground | green | " | | color4 | Foreground | blue | " | | color5 | Foreground | cyan | " | | color6 | Foreground | yellow | " | | color7 | Foreground | magenta | " | | color8 | Foreground | purple | " | | color9 | Foreground | darkslategray | " | | copyOnResize | Boolean | True | Copy raster when resized | | crosshairCursorColor | Foreground | red | Full-screen cursor color | | defaultMarker | String | rectangle | Default marker type | | deiconifyWindow | Boolean | False | Deiconify window when active | | dialogBgColor | Foreground | yellow | Status line background color | | dialogFgColor | Foreground | black | Status line foreground color | | dialogFont1 | XFontStruct | nil2 | Status line fonts | | dialogFont2 | XFontStruct | 5x8 | " | | dialogFont3 | XFontStruct | 6x10 | " | | dialogFont4 | XFontStruct | 7x13 | " | | dialogFont5 | XFontStruct | 8x13 | " | | dialogFont6 | XFontStruct | 9x15 | " | | dialogFont7 | XFontStruct | 9x15 | " | | dialogFont8 | XFontStruct | 9x15 | " | | ginmodeBlinkInterval | Int | 0 | Graphics cursor blink interval | | ginmodeCursor | String | full\_crosshair | Graphics cursor type | | ginmodeCursorBgColor | Foreground | black | Graphics cursor background color | | ginmodeCursorFgColor | Foreground | white | Graphics cursor foreground color | | height | Dimension | 480 | Height of graphics window | | idleCursor | String | Plus | Idle cursor type | | idleCursorBgColor | Foreground | white | Idle cursor background color | | idleCursorFgColor | Foreground | black | Idle cursor foreground color | | markerBoxKnotColor | Foreground | blue | Vertex knot color | | markerBoxKnotSize | Int | 0 | Vertex knot size | | markerBoxLineColor | Foreground | green | Marker border color | | markerCircleKnotColor | Foreground | blue | Vertex knot color | | markerCircleKnotSize | Int | 0 | Vertex knot size | | markerCircleLineColor | Foreground | green | Marker border color | | markerCursorBgColor | Foreground | black | Cursor background when in marker | | markerCursorFgColor | Foreground | yellow | Cursor foreground when in marker | | markerEllipseKnotColor | Foreground | blue | Vertex knot color | | markerEllipseKnotSize | Int | 0 | Vertex knot size | | markerEllipseLineColor | Foreground | green | Marker border color | | markerFill | Boolean | False | Flood fill marker area with *markerFillColor* | | markerFillBgColor | Foreground | black | Fill area background color | | markerFillColor | Foreground | slategray | Flood fill color | | markerFillStyle | Int | FillSolid | Fill area style | | markerHighlightColor | Foreground | green | Marker highlight color | | markerHighlightWidth | Int | 2 | Marker highlight line width | | markerLineKnotColor | Foreground | blue | Vertex knot color | | markerLineKnotSize | Int | 5 | Vertex knot size | | markerLineLineColor | Foreground | green | Line marker color | | markerLineStyle | Int | LineSolid | Line marker line style | | markerLineWidth | Int | 1 | Line marker width | | markerPgonKnotColor | Foreground | blue | Vertex knot color | | markerPgonKnotSize | Int | 5 | Vertex knot size | | markerPgonLineColor | Foreground | green | Marker border color | | markerRectKnotColor | Foreground | blue | Vertex knot color | | markerRectKnotSize | Int | 0 | Vertex knot size | | markerRectLineColor | Foreground | green | Marker border color | | markerTextBgColor | Foreground | slategray | Text marker background color | | markerTextBorder | Int | 2 | Text marker border width | | markerTextColor | Foreground | yellow | Text marker text color | | markerTextFont | XFontStruct | 6x13 | Text marker font | | markerTextLineColor | Foreground | green | Text marker line color | | markerTextString | String | NULL | Text string | | markerTranslations | String | default | Marker event-to-actions translations | | maxColors | Int | 216 | Max colors in custom colormap | | maxMappings | Int | 32 | Max image mappings | | maxRasters | Int | 512 | Max image rasters | | nearEdge | Int | 1 | Distance, in pixels, between pointer and marker edge required for translation actions for be in effect. | | nearVertex | Int | 4 | Distance, in pixels between pointer and marker vertex (i.e. *knot*) required for translation actions for be in effect. | | raiseWindow | Boolean | False | Raise window when active | | translations | String | default | Event-to-actions translations | | useTimers | Boolean | True | Ok to use timers | | warpCursor | Boolean | False | Enable warp cursor when active | | width | Dimension | 640 | Height of graphics window | | xorFill | Boolean | False | Fill with GXxor | | xorFillBgColor | Int | 255 | Xor-fill background color | | xorFillColor | Int | 2 | Xor-fill color | ## GTERM WIDGET TRANSLATIONS AND ACTIONS The default translations for a Gterm window are: | | | | --- | --- | | \: | m\_create() | | \: | crosshair(on) | | \: | crosshair(on) | | \: | crosshair(off) | | \: | enter-window() | | \: | leave-window() | | \: | graphics-input() | | \: | track-cursor() | The available action procedures for a Gterm window are: - *ignore()* Ignore an event. - *graphics-input()* Handle a graphics input request. - *crosshair(on\|off)* Display a crosshair cursor. - *track-cursor()* Track crosshair cursor position. - *enter-window()* Handle an EnterWindow event. - *leave-window()* Handle an LeaveWindow event. - *reset()* Do a soft reset of the Gterm widget. - *m\_create()* Create a new marker. Valid types include | | | | | | --- | --- | --- | --- | | *text* | line | polyline | rectangle | | box | circle | ellipse | polygon | The default is *rectangle*, if no type is given the default type specified by the *markerType* resource will be used. ## GTERM MARKER TRANSLATIONS AND ACTIONS The default translations for a marker are: | | | | --- | --- | | !Shift \: | m\_rotateResize() | | \: | m\_moveResize() | | !Shift \: | m\_raise() m\_markpos() | | \: | m\_raise() m\_markposAdd() | | \: | m\_redraw() m\_destroyNull() | | \: | m\_lower() | | \BackSpace: | m\_deleteDestroy() | | \Delete: | m\_deleteDestroy() | | \: | m\_input() | | \: | track-cursor() | Translations affect only the currently active marker, the cursor must be within *nearEdge* pixels of a marker edge, or *nearVertex* pixels of a marker vertex to take effect. The available action procedures for a marker are - *m\_create(type)* Create a new marker. Valid types include | | | | | | --- | --- | --- | --- | | *text* | line | polyline | rectangle | | box | circle | ellipse | polygon | The default is *rectangle*, if no type is given the default type specified by the *markerType* resource will be used. - *m\_destroy()* Destroy the active marker. - *m\_destroyNull()* Destroy the active marker if it is null sized. - *m\_set(attribute, value, ....)* Set a marker attribute. Valid attributes include | | | | | | --- | --- | --- | --- | | *activated* | autoRedraw | fill | fillBgColor | | fillColor | fillPattern | fillStyle | font | | height | highlightColor | imageText | knotColor | | knotSize | lineColor | lineStyle | lineWidth | | rotangle | sensitive | textBgColor | textBorder | | textColor | translations | type | visible | | width | x | y | | - *m\_raise()* Raise the active marker to the top of the display list. - *m\_lower()* Lower the active marker to the bottom of the display list. - *m\_notify(event, event, ....)* Notify any clients that have registered callbacks for the specified type of events. Recognized events include | | | | | --- | --- | --- | | *notify* | *moveResize* | *modify* | | *redraw* | *destroy* | *input* | | *focusIn* | *focusOut* | *constraint* | - *m\_input()* Notify any clients that have registered a input callback that a input event has occurred. - *m\_markpos()* Mark the current position of the marker, e.g., so that it can later be erased. - *m\_markposAdd()* Execute either the markpos or add action, depending upon the pointer location. If the pointer is over an active marker at a location where the add action can be executed this is done, otherwise the markpos action is executed. - *m\_redraw()* Redraw the active marker. - *m\_addPt()* Add a point (i.e. vertex knot). *Polyline* and *polygon* markers only. - *m\_deletePt()* Delete a point (i.e. vertex knot). - *m\_movePt()* Move a point (i.e. vertex knot). *Polyline* and *polygon* markers only. - *m\_deleteDestroy()* Delete a point or destroy a marker, depending upon the pointer position. - *m\_move()* Move a marker. - *m\_resize()* Resize a marker. - *m\_moveResize()* Move a point or marker, or resize a marker, depending upon the pointer position. - *m\_rotate()* Rotate a marker. - *m\_rotateResize()* Rotate or resize a marker. A marker is rotated if near a vertex know, or resized if near an edge. ## GTERM I/O ESCAPE SEQUENCES XGterm uses escape sequences to provide graphics emulation. This protocol is an extension of the Tektronix 4012 graphics protocol. The basic extensions are patterned after the Retrographics VT640 graphics terminal, using GS (octal \\035, aka Ctrl-\]) and CAN (octal \\030, aka Ctrl-x) to switch between vt100 and graphics modes. Additional extensions are defined to support advanced features such as color, area fills, graphics erasure, setting the cursor location under program control, interactive dialog via the "status line", and so on. While these escape sequences can be used directly, the best programmatic interface is to use the OBM (*Object Manager*) library supplied with the XGterm source as part of the X11IRAF package. Any Tektronix-compatible graphics library will suffice for producing vector graphics, the added escape sequences used by the Gterm widget are required to make use of imaging, area fills, the status line, etc. All escape sequences begin with an **ESC** character (octal \\033), followed by up to three characters defining the action to be taken. All strings in capital letters refer to the ASCII code (e.g. *LF* is the ASCII linefeed code), a three digit number preceded by a 'ยด refers to an octal code (e.g. " 12" is octal 12) , all others are characters in the escape code (e.g. "/bc" are the three characters '/', 'b', and 'c'). ### ESCAPE SEQUENCES - **US** - **CR** Switch to alpha mode. Characters are drawn in the graphics window at the "current" position (normally set beforehand with a GS/US vector move), using the alpha mode font. Receipt of any control code causes alpha mode to be exited. - **GS** Switch to vector polyline mode. - **FS** Switch to vector polypoint mode. - **RS** Switch to vector mode, vertices are joined as a polygon. With all three codes, vertices and points are accumulated in a buffer and displayed when the buffer fills or when vector mode is terminated by receipt of any control code. A workstation open will be done if it hasn't already been opened, no-op sequences GS-CAN are filtered out, since they would only cause a pointless switch to the graphics frame and back without drawing. The open workstation sequence is GS,US, or by the *xterm* graphics start escape sequence "\[?38h". - **EM** Enter message mode. In message mode input text is accumulated in a buffer and eventually passed to the object manager, which delivers the message to the referenced object. Messages are used to download the user interface to be executed by the object manager. During execution, messages are used to set the values of user interface parameters to allow the UI to track the state of the client application. - **CAN** Close workstation and enter command mode. - **BEL** Ring the screen bell. - **ENQ** Return terminal status. Returned values include the terminal mode, and alpha cursor x and y position. - **SUB** Initiate a cursor read, values are returned in window coordinates. - **/SUB** Return window cursor position in raster coordinates. - **FF** Clear the screen. - **/f** Set current cursor position. - **0** Set character size 0. (Currently ignored). - **1** Set character size 1. (Currently ignored). - **2** Set character size 2. (Currently ignored). - **3** Set character size 3. (Currently ignored). - **/0d** Set color index. - **/1d** Clear graphics screen. - **/2d** Invert graphics screen - **\`** Select line style 0. (Solid) - **a** Select line style 1. (Dashed) - **b** Select line style 2. (Dotted) - **c** Select line style 3. (DashDot) - **d** Select line style 4. (Dash3Dot) - **/0w** Select line width 0. - **/1w** Select line width 1. - **/2w** Select line width 2. - **/nw** Select line width 3. - **/0c** Select line color 0. - **/1c** Select line color 1. - **/2c** Select line color 2. - **/3c** Select line color 3. - **/4c** Select line color 4. - **/5c** Select line color 5. - **/6c** Select line color 6. - **/7c** Select line color 7. - **/8c** Select line color 8. - **/9c** Select line color 9. ### IMAGING ESCAPE SEQUENCES These are encoded as follows: **ESC** \ \[ *P ; P* ; ... \] \<*data*\> where *code* is a character sequence and *P* is an ASCII encoded parameter described below. - **/nc** Select line color. Parameter is the color number in the range 0-9. - **sre** *Reset*. Parameters are "reset-str". - **ssz** *Resize*. Parameters are "resize-str". - **rir** *Initialize raster*. - **rcr** *Create a raster*. Parameters are raster number, type, width, height, and depth. Type is 1 for a normal (client) raster, 2 for cached in server memory, or 0 if you don't care. Depth may be 1, 8, 16, or 32. - **rde** *Destroy a raster*. Parameter is raster number. - **rqr** *Query a raster*. Parameter is raster number. Output parameters are status, type, width, height, and depth encoded in the string ""\\033\[5;%d;%d;%d;%d;%d\]". - **rsr** *Select a raster*. Parameter is raster number. - **rwr** *Write pixels to a rectangular region of a raster*. Parameters are raster number, encoding type (not used), x1, y1, nx, ny, and depth followed by (nx\*ny) data pixels. - **rrd** *Read from a rectangular region of a raster*. Parameters are raster number, encoding type (not used), x1, y1, nx, ny, and depth followed by (nx\*ny) data pixels. - **rrp** *Refresh raster pixels*. Parameters are raster number, coordinate type (0 for pixel, 1 for NDC), x1, y1, nx, ny. - **rsp** *Set all the raster pixels in a region to a single color*. Parameters are raster number, coordinate type (0 for pixel, 1 for NDC), x1, y1, nx, ny, color, and raster operand. If nx=ny=0 the entire raster will be written. Raster operands include transient (octal 020), refresh\_all (octal 040), or refresh\_none (octal 100). - **rco** *Copy a region of the source raster to a region of the* *destination raster*. Parameters are raster operand, source raster number, source type, source x coord, source y coord, source width, source height, destination raster number, destination type, destination x coord, destination y coord, destination width, destination height, If the input and output regions are not the same size the subimage is automatically scaled to fit the destination region. If the destination extent DNX or DNY is negative, the image is flipped in that axis. The type of spatial scaling performed is determined by the scale factors (zoom, dezoom, or no scaling). The rasterop argument is used to exercise fine control over how the mapping is performed, e.g. to force a refresh, implement a transient mapping, or in the case of a dezoom (many-to-one) mapping, select the antialiasing technique to be used. - **rwc** *Write a colormap*. Parameters are colormap number, first color and the number of colors followed by NC colors triples in the data. - **rrc** *Return the color assignments for a region of the named colormap*. Parameters are colormap number, first color and the number of colors followed by NC colors triples in the data. - **rlc** *Load a colormap into the display*, optionally scaling the colormap via a linear transformation in the process. Parameters are the colormap number, the offset value, and the cursor x and Y coordinates in NDC units. The colormap is unaffected if offset=0.5, scale=1.0. A negative scale inverts the image. If map=0 the linear transformation is applied directly to the display colormap. - **rfc** *Free a colormap*. Parameter is the colormap number. - **rwo** *Write the IOmap*. Parameters are the first color and the number of colors, followed by NC color triples in the data. An iomap is an optional lookup table used to isolate the client application from the color model used within the Gterm widget. To simplify color allocation the Gterm widget defines a logical color space where color 0 is the background, 1 the foreground, 2-N are statically allocated standard colors, and colors N+1 and above are dynamically allocated by the graphics application. Less-demanding applications use only the statically allocated, shared colors. The widget internally maps these logical colors to whatever the window system requires, but providing a well-defined logical color space isolates the client from the details of color allocation in the underlying window system. An iomap can be used to define a mapping between the color model of the client application and the Gterm color model (when we say color model here we mean color allocation schemes for 8 bit pseudocolor). By default the iomap is one-to-one. The use of an iomap frees the client from having to worry about color index translations, and allows color tables to be combined in the widget for greater efficiency when color tables are serially applied. The iomap applies to all color indices or pixel values passed in i/o operations between the client and the Gterm widget. - **rro** *Read the IOmap*. Return values are the first color and the number of colors, followed by NC color triples in the data. - **rim** *Delete all mappings* and initialize the mapping subsystem. - **rsm** *Define a new mapping function*, or modify an old one. If a new mapping is defined it is merely enabled, and no refreshing of the screen takes place until either some mapped data is written to or the mapping is explicitly refreshed. If an existing mapping is modified the old and new mappings are examined and only those portions of the destination rect for which the mapping changed are updated. This permits minor changes to a mapping (e.g. moving an edge) without having to redraw the entire region. Regions of the destination drawable which were previously covered by the mapping but which were exposed by modifying the mapping are redrawn. - **rgm** *Return the external parameters of a mapping*. Parameter is the mapping number, values returned (in the string "\\033\[6;%d;%d %d;%d;%d;%d;%d;%d %d;%d;%d;%d;%d;%d\]") are the mapping number, rasterop, source mapping, type, x, y, width, height, and destination mapping, type, x, y, width and height. - **rem** *Enable a mapping*. Parameters are the mapping number and an integer flag indicating whether to refresh the mapping. - **rdm** *Disable a mapping*. Disabling a mapping does not affect the mapping definition, hence a disabled mapping may later be reenabled. Parameters are the mapping number and an integer flag indicating whether to erase the mapping. - **rrm** *Refresh a mapping*. Parameter is the mapping number. - **rfm** *Free a mapping*. Parameter is the mapping number. ## MORE ON IMAGING The imaging model of the Gterm widget defines the following key object or data types: *rasters*, *mappings*, and *colors*. - **raster** A raster is a MxN array of pixels. At present pixels are 8 bits deep but hooks are built into the widget to expand this in the future. Pixel values are indices into the Gterm virtual colormap, with values starting at zero. A raster may be any size. A raster is merely a two-dimensional array in the graphics server; it is not displayed unless mapped. An exception is raster zero, which is the graphics window. Rasters are referred to by number, starting with zero. Initially only raster zero exists; new rasters are created with the create raster escape code **rcr**. Space for rasters may be allocated either in the graphics server, or in the X server. This has implications on performance but is otherwise transparent to the client. By default rasters are allocated in the graphics server, i.e., in the X client. - **mapping** A mapping defines a projection of a rectangle of the source raster onto a rectangle of the destination raster. Mappings may be either enabled (active) or disabled. When a mapping is enabled, any change to a pixel in the source rect will cause the corresponding pixels in the destination rect to be updated. Mappings are referred to by number starting with one. Initially no mappings are defined. If the size of the input and output rect is not the same the input rect will be scaled by pixel replication or subsampling to fill the output rect. If the argument DW (destination width) or DH (destination height) of the destination rect is negative, the image will be flipped around the corresponding axis when copied to the destination; the region of the destination drawn into is the same in either case. Multiple mappings may reference the same source or destination raster. Mappings are refreshed in order by the mapping number. Modifying a mapping causes the changed regions of the destination rect to be refreshed. - **color** The *Gterm* widget provides a fixed number of preassigned colors corresponding to pixel values 0 through 9. Zero is the background color, one is the foreground color, and 2-9 (8 colors) are arbitrary colors defined by Gterm widget resources. These static colors are normally used to draw the background, frame, axes, titles, etc. of a plot, or to draw color graphics within the drawing area. The advantage of static colors is that they are shared with other X clients, and the values of these colors may be assigned by the user to personalize the way plots look. The *Gterm* widget also allows any number (up to about 200 or so) additional colors to be defined at runtime by the client application. These color values start at pixel value 10 and go up to the maximum pixel value assigned by the client. The client application allocates colors with the write colormap escape code **rwc**. Attempts to overwrite the values of the static colors are ignored. The values of already allocated colors may be changed dynamically at runtime using write colormap code to write the desired range of color values. Applications should not assume that there are 10 static colors and 200 or so allocatable colors. The IRAF graphcap entry for the logical device in use, and resources set for the widget, defines these parameters for the device. Alternatively, the read colormap code may be used to dynamically determine how many colors the server has preallocated when the application starts up. An image may use either static and dynamic pixel values or both types of values, but in most cases imaging applications involve smoothly shaded surfaces hence will require dynamically assigned private colors. If for some reason the client application cannot use the *Gterm* widget color model, the IOMAP feature can be used to make the widget appear to have some externally defined (i.e., client defined) color model. The maximum number of rasters and maximum number of mappings is defined by the Gterm widget resources *maxRaster* and *maxMappings* (or in the GUI file) when the graphics application starts up. The maximum values should be much larger than most applications require. Applications should allocate raster or mapping numbers sequentially starting at 1 (more or less) to avoid running out of raster or mapping descriptors. The {read\|write}pixels escape codes operate directly on raster pixels. The mapping escape codes support two alternative coordinate systems, raster pixels and NDC (normalized device coordinates), as indicated by the ST or DT argument (source or destination coordinate type). Note that the origin of the pixel coordinate system is the upper left corner of the display window (consistent with most graphics systems), whereas the origin of the NDC coordinate system is the lower left corner (consistent with IRAF). Pixel coordinates allow precise control of imaging but require the application to know the window size, and may result in complications e.g. if the window is resized. NDC coordinates pretty much guarantee that a mapping will involve sampling, hence are not the most efficient, but the graphics will be drawn correctly no matter how the window is resized and for most applications the performance difference is negligible. Most applications should use NDC coordinates for raster 0 (the display window), and pixel coordinates for rasters 1-N. Although the size of rasters 1 and higher are defined by the client application, the size of raster zero, the actual gterm display window, is subject to the constraints of the window system. The client can attempt to reset the size of the gterm window using create raster escape with raster=0, however the Gterm widget, UI containing the *Gterm* widget, and the window manager are all free to deny such a request. The query raster escape should be called to determine the actual size of the window one will be drawing into. ### AN EXAMPLE IMAGING APPLICATION An example of a simple imaging application might be one that downloads an image and displays it in the gterm window, filling the window. This could be done as follows (following a graphics open and other escape codes to prepare the drawing surface). - *create raster* Create raster 1 the size of the pixel array to be displayed. This need not be the same as the size of the gterm display window. - *set mapping* Define a mapping between raster 1 and raster 0, the display window, using NDC coordinates to define the region of the display window to be filled. The mapping number is arbitrary but mappings should normally be allocated starting with 1. The mapping is automatically enabled when first defined. - *write colormap* (Optional). Define the pixel value to RGB color assignments for the image pixels. - *write pixels* This escape is called one or more times to write pixels into raster 1. At most 32K pixels can be written in each call. As each write is made the affected region of the display window will be updated. Alternatively, one could write the pixels and then define the mapping to cause the entire image to be displayed at once. Note that the imaging escape can be combined with normal graphics to draw text and graphics around or on top of an image region. The order in which drawing operations occur is important, e.g., to draw graphics or text on top of an image the image should be drawn first. ## MARKERS Markers are a general feature of the *Gterm* widget and are used more extensively in other programs (e.g. the prototype IRAF science GUI applications), but they have no real use in *xgterm* when used as simply a graphics terminal. All markers share some of the same characteristics, so it is worthwhile learning basic marker manipulation keystrokes (as defined using the default marker translations), especially how to delete an accidentally created marker: - **o** *Delete* or *Backspace* in a marker deletes it. - **o** MB1 anywhere inside a marker may be used to drag the marker. - **o** MB1 near a marker corner or edge, depending on the type of marker, resizes the marker. - **o** Shift-MB1 on the corner of most markers will rotate the marker. - **o** Markers stack, if you have several markers and you put one on top of the other. The active marker is highlighted to tell you which of the stacked markers is active. If the markers overlap, this will be marker "on top" in the stacking order. - **o** MB2 in the body of a marker "lowers" the marker, i.e. moves it to the bottom of the stacking order. ## ENVIRONMENT *XGterm* sets the environment variables \`\`TERM'' and \`\`TERMCAP'' properly for the size window you have created. It also uses and sets the environment variable \`\`DISPLAY'' to specify which bit map display terminal to use. The environment variable \`\`WINDOWID'' is set to the X window id number of the *xgterm* window. ## SEE ALSO [xterm(1)](/xterm/1.md), [resize(1)](/resize/1.md), X(1), [pty(4)](/pty/4.md), [tty(4)](/tty/4.md)\ *Xterm Control Sequences* (in the *xterm* source directory) ## BUGS Many of the same bugs affecting *xterm* also apply here. *Xgterm* is not normally installed with setuid permissions. On some Linux systems, for example, where the /dev/tty and /dev/pty devices have root ownership and permission 600 this can cause problems. Workarounds are to either install *XGterm* with setuid permissions or modify the /dev/tty and /dev/pty devices to have permission 666. ## COPYRIGHT Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.